1. The Field of the Invention
The present invention relates generally to electronic circuitry. More particularly, embodiments of the present invention relate to mechanisms for detecting the presence of received signals using a signal strength measuring differential output linear amplifier.
2. Background and Relevant Art
The ability to remotely communicate information using electronic and optical signals has contributed to monumental advancements in our ability to collaborate and access information. Communication is enabled by a transmitter at one node in a network transmitting information over a medium to a receiver at another node. Often, it is appropriate for a receiver to take one course of action if a signal is being received, and quite a different course of action if a signal is not being received. Accordingly, receivers often have a signal detect circuit that allows the receiver to detect whether or not a signal is being received.
In high speed networks, information is communicated at high frequencies. For instance, optical networks are capable of operating at frequencies in the Gigahertz range with anticipated future capabilities entering even the Terahertz range. Accordingly, circuits designed for only for low speed applications may not be suitable for optical transceivers. For instance, an optical signal detect circuit must be especially suitable for high speed applications.
Some signal detect circuits have difficulty detecting the difference between series of low states and a no signal state. Accordingly, it may be possible for a signal detect signal to give a false indication of a no signal state given certain received signal sequences. Furthermore, signal detect circuits may be sensitive to how the module is connected. For example, when receiving a differential signal, one of the signals should be coupled to a specific input terminal of the transceiver, while the other signal should be coupled to the other input terminal. The signal detect circuit may be specifically designed to work with this connection polarity. If the polarity is reversed, the signal detect circuit may not work due to the offset inherent in some of the amplifiers and/or comparators present in the signal detect circuit.
Accordingly, what would be advantageous is a signal detect circuit that is not sensitive to polarity, and which accurate detects a no signal state regardless of the signal sequence received. It would be further advantageous if the signal detect circuit was suitable for high speed communications.